The invention relates to a portable projection apparatus with an endless belt running on rollers, and a rotatable disk having a band at its outer surface with the endless belt partially embracing the band and with the projection material being accelerable between the outer surfaces of the band and the endless belt.
Federal Republic of Germany No. OS 1 073 345 discloses an apparatus for the production of a beam of granular material in which a band moves around the partial circumference of a rotating disk. It is a disadvantage of this apparatus that no continuous movement is possible since the projection material supply has to be adjusted separately by hand in order for the projection material to be grasped by the band and the disk. In the case of uneven supply of projection material, the band slips off because of the lack of a precise forced guidance, and thus there is no assurance that additional projection material will be carried along and that the apparatus is functional. This apparatus is stationarily arranged.
Such an apparatus was once built and tried by the inventor. It was confirmed that it did not work in practical use. The band did not remain on track, ran into the rims, and broke.
It is an object of the invention to provide an apparatus of the initially-mentioned type in which a secure positive guidance of the endless belt is assured so that the endless belt does not slide off from the rollers during the operation of the projection apparatus. Furthermore, a targeted projection of the projection material is to be carried out without the endless belt sliding off laterally. The retightening of the endless belt can be accomplished in a simple fashion.
The object of the invention is accomplished in that the outer surface of the band has longitudinal grooves and in that the interior surface of the endless belt has a profiling which runs parallel to the circumferential direction, into which the outer surface of the rollers, guiding the endless belt, engage with a corresponding profile.
When the band is rotating with the disk, the endless belt, which partially embraces the band, is brought along tensionally by the band, with the projection material being located between the grooves of the band and the endless belt. By rotating the band with the disk, the supplied projection material is grasped, accelerated and then projected tangentially. The endless belt is forcibly guided with its interior surface and the outer surface of the rollers, with the endless belt not being able to slide off from the roller laterally. Thus it is assured that even in the case of uneven supply of the projection material, the endless belt remains securely in its position. The projection material is accelerated between the longitudinal grooves of the band and the outer surface of the endless belt. This mode of operation resembles a belt drive, only under different conditions.
Particularly advantageous embodiments of the apparatus in the invention will be disclosed in the subordinate claims.